// Copyright (c) 2012 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "base/time/time.h"

#include <CoreFoundation/CFDate.h>
#include <CoreFoundation/CFTimeZone.h>
#include <mach/mach.h>
#include <mach/mach_time.h>
#include <stddef.h>
#include <stdint.h>
#include <sys/sysctl.h>
#include <sys/time.h>
#include <sys/types.h>
#include <time.h>

#include "base/logging.h"
#include "base/mac/mach_logging.h"
#include "base/mac/scoped_cftyperef.h"
#include "base/mac/scoped_mach_port.h"
#include "base/macros.h"
#include "base/numerics/safe_conversions.h"
#include "build/build_config.h"

namespace {

int64_t ComputeCurrentTicks()
{
#if defined(OS_IOS)
    // On iOS mach_absolute_time stops while the device is sleeping. Instead use
    // now - KERN_BOOTTIME to get a time difference that is not impacted by clock
    // changes. KERN_BOOTTIME will be updated by the system whenever the system
    // clock change.
    struct timeval boottime;
    int mib[2] = { CTL_KERN, KERN_BOOTTIME };
    size_t size = sizeof(boottime);
    int kr = sysctl(mib, arraysize(mib), &boottime, &size, nullptr, 0);
    DCHECK_EQ(KERN_SUCCESS, kr);
    base::TimeDelta time_difference = base::Time::Now() - (base::Time::FromTimeT(boottime.tv_sec) + base::TimeDelta::FromMicroseconds(boottime.tv_usec));
    return time_difference.InMicroseconds();
#else
    static mach_timebase_info_data_t timebase_info;
    if (timebase_info.denom == 0) {
        // Zero-initialization of statics guarantees that denom will be 0 before
        // calling mach_timebase_info.  mach_timebase_info will never set denom to
        // 0 as that would be invalid, so the zero-check can be used to determine
        // whether mach_timebase_info has already been called.  This is
        // recommended by Apple's QA1398.
        kern_return_t kr = mach_timebase_info(&timebase_info);
        MACH_DCHECK(kr == KERN_SUCCESS, kr) << "mach_timebase_info";
    }

    // mach_absolute_time is it when it comes to ticks on the Mac.  Other calls
    // with less precision (such as TickCount) just call through to
    // mach_absolute_time.

    // timebase_info converts absolute time tick units into nanoseconds.  Convert
    // to microseconds up front to stave off overflows.
    base::CheckedNumeric<uint64_t> result(
        mach_absolute_time() / base::Time::kNanosecondsPerMicrosecond);
    result *= timebase_info.numer;
    result /= timebase_info.denom;

    // Don't bother with the rollover handling that the Windows version does.
    // With numer and denom = 1 (the expected case), the 64-bit absolute time
    // reported in nanoseconds is enough to last nearly 585 years.
    return base::checked_cast<int64_t>(result.ValueOrDie());
#endif // defined(OS_IOS)
}

int64_t ComputeThreadTicks()
{
#if defined(OS_IOS)
    NOTREACHED();
    return 0;
#else
    base::mac::ScopedMachSendRight thread(mach_thread_self());
    mach_msg_type_number_t thread_info_count = THREAD_BASIC_INFO_COUNT;
    thread_basic_info_data_t thread_info_data;

    if (thread.get() == MACH_PORT_NULL) {
        DLOG(ERROR) << "Failed to get mach_thread_self()";
        return 0;
    }

    kern_return_t kr = thread_info(
        thread.get(),
        THREAD_BASIC_INFO,
        reinterpret_cast<thread_info_t>(&thread_info_data),
        &thread_info_count);
    MACH_DCHECK(kr == KERN_SUCCESS, kr) << "thread_info";

    base::CheckedNumeric<int64_t> absolute_micros(
        thread_info_data.user_time.seconds + thread_info_data.system_time.seconds);
    absolute_micros *= base::Time::kMicrosecondsPerSecond;
    absolute_micros += (thread_info_data.user_time.microseconds + thread_info_data.system_time.microseconds);
    return absolute_micros.ValueOrDie();
#endif // defined(OS_IOS)
}

} // namespace

namespace base {

// The Time routines in this file use Mach and CoreFoundation APIs, since the
// POSIX definition of time_t in Mac OS X wraps around after 2038--and
// there are already cookie expiration dates, etc., past that time out in
// the field.  Using CFDate prevents that problem, and using mach_absolute_time
// for TimeTicks gives us nice high-resolution interval timing.

// Time -----------------------------------------------------------------------

// Core Foundation uses a double second count since 2001-01-01 00:00:00 UTC.
// The UNIX epoch is 1970-01-01 00:00:00 UTC.
// Windows uses a Gregorian epoch of 1601.  We need to match this internally
// so that our time representations match across all platforms.  See bug 14734.
//   irb(main):010:0> Time.at(0).getutc()
//   => Thu Jan 01 00:00:00 UTC 1970
//   irb(main):011:0> Time.at(-11644473600).getutc()
//   => Mon Jan 01 00:00:00 UTC 1601
static const int64_t kWindowsEpochDeltaSeconds = INT64_C(11644473600);

// static
const int64_t Time::kWindowsEpochDeltaMicroseconds = kWindowsEpochDeltaSeconds * Time::kMicrosecondsPerSecond;

// Some functions in time.cc use time_t directly, so we provide an offset
// to convert from time_t (Unix epoch) and internal (Windows epoch).
// static
const int64_t Time::kTimeTToMicrosecondsOffset = kWindowsEpochDeltaMicroseconds;

// static
Time Time::Now()
{
    return FromCFAbsoluteTime(CFAbsoluteTimeGetCurrent());
}

// static
Time Time::FromCFAbsoluteTime(CFAbsoluteTime t)
{
    static_assert(std::numeric_limits<CFAbsoluteTime>::has_infinity,
        "CFAbsoluteTime must have an infinity value");
    if (t == 0)
        return Time(); // Consider 0 as a null Time.
    if (t == std::numeric_limits<CFAbsoluteTime>::infinity())
        return Max();
    return Time(static_cast<int64_t>((t + kCFAbsoluteTimeIntervalSince1970) * kMicrosecondsPerSecond) + kWindowsEpochDeltaMicroseconds);
}

CFAbsoluteTime Time::ToCFAbsoluteTime() const
{
    static_assert(std::numeric_limits<CFAbsoluteTime>::has_infinity,
        "CFAbsoluteTime must have an infinity value");
    if (is_null())
        return 0; // Consider 0 as a null Time.
    if (is_max())
        return std::numeric_limits<CFAbsoluteTime>::infinity();
    return (static_cast<CFAbsoluteTime>(us_ - kWindowsEpochDeltaMicroseconds) / kMicrosecondsPerSecond) - kCFAbsoluteTimeIntervalSince1970;
}

// static
Time Time::NowFromSystemTime()
{
    // Just use Now() because Now() returns the system time.
    return Now();
}

// static
bool Time::FromExploded(bool is_local, const Exploded& exploded, Time* time)
{
    base::ScopedCFTypeRef<CFTimeZoneRef> time_zone(
        is_local
            ? CFTimeZoneCopySystem()
            : CFTimeZoneCreateWithTimeIntervalFromGMT(kCFAllocatorDefault, 0));
    base::ScopedCFTypeRef<CFCalendarRef> gregorian(CFCalendarCreateWithIdentifier(
        kCFAllocatorDefault, kCFGregorianCalendar));
    CFCalendarSetTimeZone(gregorian, time_zone);
    CFAbsoluteTime absolute_time;
    // 'S' is not defined in componentDesc in Apple documentation, but can be
    // found at http://www.opensource.apple.com/source/CF/CF-855.17/CFCalendar.c
    CFCalendarComposeAbsoluteTime(
        gregorian, &absolute_time, "yMdHmsS", exploded.year, exploded.month,
        exploded.day_of_month, exploded.hour, exploded.minute, exploded.second,
        exploded.millisecond);
    CFAbsoluteTime seconds = absolute_time + kCFAbsoluteTimeIntervalSince1970;

    base::Time converted_time = Time(static_cast<int64_t>(seconds * kMicrosecondsPerSecond) + kWindowsEpochDeltaMicroseconds);

    // If |exploded.day_of_month| is set to 31
    // on a 28-30 day month, it will return the first day of the next month.
    // Thus round-trip the time and compare the initial |exploded| with
    // |utc_to_exploded| time.
    base::Time::Exploded to_exploded;
    if (!is_local)
        converted_time.UTCExplode(&to_exploded);
    else
        converted_time.LocalExplode(&to_exploded);

    if (ExplodedMostlyEquals(to_exploded, exploded)) {
        *time = converted_time;
        return true;
    }

    *time = Time(0);
    return false;
}

void Time::Explode(bool is_local, Exploded* exploded) const
{
    // Avoid rounding issues, by only putting the integral number of seconds
    // (rounded towards -infinity) into a |CFAbsoluteTime| (which is a |double|).
    int64_t microsecond = us_ % kMicrosecondsPerSecond;
    if (microsecond < 0)
        microsecond += kMicrosecondsPerSecond;
    CFAbsoluteTime seconds = ((us_ - microsecond) / kMicrosecondsPerSecond) - kWindowsEpochDeltaSeconds - kCFAbsoluteTimeIntervalSince1970;

    base::ScopedCFTypeRef<CFTimeZoneRef> time_zone(
        is_local
            ? CFTimeZoneCopySystem()
            : CFTimeZoneCreateWithTimeIntervalFromGMT(kCFAllocatorDefault, 0));
    base::ScopedCFTypeRef<CFCalendarRef> gregorian(CFCalendarCreateWithIdentifier(
        kCFAllocatorDefault, kCFGregorianCalendar));
    CFCalendarSetTimeZone(gregorian, time_zone);
    int second, day_of_week;
    // 'E' sets the day of week, but is not defined in componentDesc in Apple
    // documentation. It can be found in open source code here:
    // http://www.opensource.apple.com/source/CF/CF-855.17/CFCalendar.c
    CFCalendarDecomposeAbsoluteTime(gregorian, seconds, "yMdHmsE",
        &exploded->year, &exploded->month,
        &exploded->day_of_month, &exploded->hour,
        &exploded->minute, &second, &day_of_week);
    // Make sure seconds are rounded down towards -infinity.
    exploded->second = floor(second);
    // |Exploded|'s convention for day of week is 0 = Sunday, i.e. different
    // from CF's 1 = Sunday.
    exploded->day_of_week = (day_of_week - 1) % 7;
    // Calculate milliseconds ourselves, since we rounded the |seconds|, making
    // sure to round towards -infinity.
    exploded->millisecond = (microsecond >= 0) ? microsecond / kMicrosecondsPerMillisecond : (microsecond - kMicrosecondsPerMillisecond + 1) / kMicrosecondsPerMillisecond;
}

// TimeTicks ------------------------------------------------------------------

// static
TimeTicks TimeTicks::Now()
{
    return TimeTicks(ComputeCurrentTicks());
}

// static
bool TimeTicks::IsHighResolution()
{
    return true;
}

// static
TimeTicks::Clock TimeTicks::GetClock()
{
#if defined(OS_IOS)
    return Clock::IOS_CF_ABSOLUTE_TIME_MINUS_KERN_BOOTTIME;
#else
    return Clock::MAC_MACH_ABSOLUTE_TIME;
#endif // defined(OS_IOS)
}

// static
ThreadTicks ThreadTicks::Now()
{
    return ThreadTicks(ComputeThreadTicks());
}

} // namespace base
